The present invention relates to a receiver system for receiving and detecting electromagnetic signals and, in particular, to a channelizing receiver system for receiving and detecting electromagnetic signals and for providing information regarding the characteristics of these signals. The present invention also relates to a method for detecting and characterizing electromagnetic signals using a channelized receiver system.
Systems for scanning and detecting a wide range of electromagnetic signals and, in particular radio frequency (RF) signals, and for analyzing the detected signals are widely used for electronic warfare (EW) and for other military and non-military applications. Systems performing such functions may employ a searching system and an analyzing system. A channelizing receiver often is used for the searching system.
A channelizing receiver typically includes a number of uniformly spaced, narrow bandwidth receivers which together contiguously cover the entire electromagnetic spectrum of interest. Each narrow bandwidth receiver (channel receiver) typically includes a log detector, for converting RF emissions into a log video signal, and a threshold detector for evaluating the signal generated by the log detector. The particular channel receiver of the channelizing receiver providing an output signal provides a rough estimate of a detected signal's time of arrival, pulse width and frequency. If several channel receivers provide output signals, the output signal having the greatest magnitude may be used to provide this rough estimate.
Information from the channelizing receiver often is transmitted to an analyzing receiver. The analyzing receiver performs a more extensive analysis of the particular signal to precisely measure the signal's frequency, bandwidth and pulse width and also to determine the signal's phase and modulation. The information from the channelizing receiver, however, enables the analyzing receiver to perform this function more efficiently and effectively. By screening noise and other signals of no interest, the channelizing receiver enables the analyzing receiver to focus only on the signals of importance.
Current channelizing receivers suffer, however, from a number of deficiencies. First, each channel receiver must be capable of detecting the majority of electromagnetic emissions within its designated bandwidth. As a result, the channel receiver cannot be optimized for both short duration electromagnetic signals and long duration electromagnetic signals.
Second, since each channel receiver monitors a contiguous segment of a broad electromagnetic spectrum, an electromagnetic signal can trigger output signals from several channel receivers. As a result, the analyzing system must direct resources, at least temporarily, to resolve where in the frequency spectrum the signal is located, and the analyzing system often is delayed in directing resources to the signal or signals of real interest.
Third, as a result of noise and modulation of a signal's rising and falling edges, an individual channel receiver can falsely report multiple detections from a single incoming signal. These false detections also waste the resources of the analyzing system.
As a final matter, the configuration of current channelizing receivers imposes inherent limitations on signal-to-noise sensitivity and on the quality of information provided to the analyzing system. These inherent limitations reduce the overall quality and reliability of these systems.